The present invention relates generally to recording heads used in magnetic media storage devices, and more particularly to magneto-resistive disk drive heads.
Disk drives containing Giant Magneto-Resistive (GMR) heads typically are supported above a disk drive surface by a thin film of air. The Air Bearing Surface (ABS) of the head flies above the disk surface by the air layer produced by the rotation of the disk surface beneath the head. Since the sensitivity of the head sensor depends on the gap spacing of the ABS above the disk surface, it is desirable that this gap distance be as small as possible, in order to produce the maximum sensitivity in the sensor. The typical gap spacing is currently as small as 0.6 micro-inch (10xe2x88x926 inch). At such close distances, the slightest surface irregularity can cause the ABS to contact the disk surface at least briefly. Typical proximity recording sliders made using inductive transducer technology are subjected to large amounts of substrate and transducer wear during the initial hours of the drive operational life. Currently, fly heights of GMR heads have reaching a point where some level of interference is required, and similar levels of wear on some heads will be expected. This process, wherein the head is expected to contact points on the disk surface and thereby remove these higher points is commonly referred to as xe2x80x9cdrive burnishingxe2x80x9d.
To reduce wear on the sensitive transducer elements, a protective coating, typically of some very hard substance such as Diamond-Like Carbon (DLC) is used, but again, by interposing this protective layer, the separation distance between the transducer sensor and the disk surface is necessarily increased, with an attendant decrease in sensitivity. Therefore, to maximize performance of GMR heads, the DLC protective layer has typically been reduced in thickness to less than 0.2 micro-inch. With such a thin protective layer, any wear of the surface of the GMR element, will expose the transducer structure to the drive environment.
In addition, the magneto-resistive head operates by passing a voltage differential across the sensor element, so that changes in the resistance of the element in response to magnetic field changes by domains on the disk are used to read data. When the protective layer is abraded away, the voltage differential across the element will cause some level of unprotected shorting to the disc in areas where the media carbon is absent.
GMR elements are similar in material composition to previous Anisotrophic Magneto-Resistive (AMR) heads, with the exception of several spacer layers, including copper. Although copper which is protected by an intact DLC layer generally does not corrode, it has been determined that exposed copper is subject to corrosive attack at the air-bearing surface, either during head fabrication or while in the disc drive (due to pin-holes or damage to the DLC). In order to decrease corrosion of the copper when the DLC is damaged, typical solutions rely on drive chemical filters and residual disc lubricant to protect this critical layer. These solutions provide less complete protection to the copper than an intact DLC layer.
Thus there is a need for a magneto-resistive head transducer which can include elements made of copper, but which is not subject to corrosion when a protective DLC becomes damaged due to very close proximity operation, and which does not rely on drive chemical filters and residual disc lubricant to protect the transducer. Additionally, there is a need for a GMR head which has less potential for transducer-to-disc shorting as the DLC layer becomes damaged.
Measurements show that current GMR heads are not strongly sensitive to flux decay through the GMR element from the ABS to the top side. FIG. 8 shows the normalized amplitude vs.stripe height of the copper layer for a group of parts. The stripe height (SH) is symbolized by the triangle markers, measured in microinches, the flux, J, is indicated by squares, and the total by diamonds. The graph shows that as the strip height is varied, the amplitude of the sensor response is little changed, whereas variations in the flux affect the amplitude greatly, indicating that current density is the key parameter in determining amplitude.
Because of this effect, some small part of the copper element can be purposely sacrificed at the ABS, by purposely removing the copper layer for some controlled distance inside the transducer. This area is then filled in with an inert protective material (such as carbon or Si) during slider fabrication. The depth of this copper removal area is sufficient, such that the drive burnishing process will not re-expose copper material. The removed copper area effectively becomes a nano-scopic flux guide design, wherein no signal is generated in this area, and some current shunting does occur. Based on the data in FIG. 8, the amount of signal loss will be less than 10% (Cu removal depth of 1 micro-inch, for a total stripe height of 10-15 micro-inch). This effect will be reduced during the burnishing process.
A second concern for exposure during the burnishing process is potential for current spiking to the disc. Current spiking in general is not catastrophic for the head (at least with AMR), but is a very difficult condition for the electronics to recover from. In addition, for a proximity head, if there is one area on the disc where this occurs, spiking could affect many tracks due to the width of exposed leads at the ABS. Thus a second application of the present invention is to preferentially etch back most of the lead area at the ABS to recess it by 1 micro-inch (a similar depth of recessed area to that used on the copper layer), and refill this area with a dielectric material.
This specification discloses a method for producing a disk drive head that will not be subject to corrosive attack, after the surface layer of DLC is damaged by forming a recessed area which is then filled with protective material to a depth greater than the depth of material typically burnished off from the ABS. In addition, a method for reducing the potential for transducer-to-disc shorting is described by forming a recessed area in the proximal portions of electrical leads, the recessed area then being similarly filled with protective dielectric material to a depth greater than that typically removed by drive burnishing. Also disclosed is a slider made by using one or both of these methods.
Accordingly, it is an object of the present invention to provide a recording head that will not be subject to corrosive attack, after the surface layer of DLC is removed or damaged.
Another object of the invention is to reduce the potential for transducer-to-disc shorting.
And another object of the invention is to provide a recording head that does not require drive chemical filters and residual disc lubricant to protect the copper layer.
Briefly, one preferred embodiment of the present invention is a slider for reading data from a disk surface, the slider including a magneto-resistive head. The head includes a magnetic transducer having a stack of layers, each layer having a proximal end proximal to the disk surface, and a pair of electrical leads, connected to the transducer, each one of the electrical leads also having a proximal end proximal to the disk surface. At least one of the proximal ends of the electrical leads and the layers is recessed to provide one or more recessed areas. The recessed areas are then filled with protective material to a depth such that when the layer of protective material is worn from the proximal ends by burnishing by the disk surface, protective material still remains in the recessed areas.
Also disclosed is a method of fabrication of a slider having recessed areas filled with protective material which protect materials from corrosion and electrical spiking.
An advantage of the present invention is that it does not rely on drive chemical filters and residual disc lubricant to protect the transducer.
Another advantage of the invention is the fly height of the slider can be minimized without risking damage to the copper element by corrosion.
And another advantage of the invention is current spiking to the disk is minimized.
These and other objects and advantages of the present invention will become clear to those skilled in the art in view of the description of the best presently known mode of carrying out the invention and the industrial applicability of the preferred embodiment as described herein and as illustrated in the several figures of the drawings.